Characteristics of sodium and water retention in rats with nephrotic syndrome induced by puromycin aminonucleoside

Introduction: Nephrotic syndrome (NS) is characterized by renal sodium and water retention. The mechanisms are not fully elucidated.

Methods: The NS rat model was established by single intraperitoneal injection of 100 mg/kg puromycin aminonucleoside (PAN). The plasma electrolyte level and urinary sodium excretion were monitored dynamically. The changes of some sodium transporters, including epithelial Na⁺ channel (ENaC), Na⁺/H⁺ exchanger 3 (NHE3), Na⁺-K⁺-2Cl^- cotransporter 2 (NKCC2) and Na⁺-Cl^- cotransporter (NCC) in renal cortex at different time points and the level of peripheral circulation factors were detected.

Results: The urinary sodium excretion of the model group increased significantly on the first day, then decreased compared with the control group, and there was no significant difference between the model group and the control group on the 12th day. The changes of peripheral circulation factors were not obvious. Some sodium transporters in renal cortex increased in varying degrees, while NKCC2 decreased significantly compared with the control group.

Conclusions: The occurrence of NS edema may not be related to the angiotensin system. The decrease of urinary sodium excretion is independent of the development of albuminuria. During the 18 days of observation, it can be divided into three stages: sodium retention, sodium compensation, and simple water retention. The mechanism is related to the increased expression of α-ENaC, γ-ENaC, NHE3 and NCC in a certain period of time, the compensatory decrease of NKCC2 expression and the continuous increase of Aquaporin 2 (AQP2) expression.

Aquaporin 2; Epithelial Na+ channel; Nephrotic syndrome; Sodium and water retention; Urinary sodium excretion.